Codeless tracking of GNSS signals implies the ability to track, and generate measurements from, spread spectrum signals without knowing the spreading codes. The approach has traditionally been applied to the GPS P-code, in order to extract dual frequency measurements in civil receivers. More recently, the technique has been proposed for quality monitoring of BOC signals, such as the Galileo Public Regulated Service (PRS).
In this paper, we present an extension to the codeless tracking approach that permits both code and sub-carrier delay measurements to be made. These measurements can be tracked independently, for example using a Double Estimator (DE) like structure. This in turn, allows high precision code measurements to be made even without knowing the code chips, albeit with an ambiguity of one code chip. Alternatively, the approach can be used to augment the BOC signal quality monitoring concept, by providing measurements of the code/sub-carrier divergence.
The validity of the approach is demonstrating on PRS data generated using a Spirent signal simulator, for which the code chips are known. This permits a direct comparison between coded and codeless tracking. The utility of the approach is also demonstrated on real broadcast Galileo data collected at the JRC using a wideband antenna and RF front-end.